1. Field of the Invention
The present invention relates to a carbon-dioxide-gas absorber that absorbs a carbon dioxide gas at high temperatures, is regenerated by evolution of the absorbed carbon dioxide gas under predetermined conditions, and thus can be repeatedly used; a method for separating a carbon dioxide gas using the absorber; and an apparatus for separating a carbon dioxide gas including the absorber.
2. Description of the Related Art
Multilayer ceramic electronic components, such as multilayer ceramic capacitors, are typically produced by, for example, forming a ceramic slurry primarily including a dielectric material powder, such as barium titanate, into sheets, forming electrodes on the resulting ceramic green sheets (dielectric sheets) by printing, and stamping the sheets into required portions and laminating the resulting portions.
In some cases, unnecessary portions after stamping the ceramic green sheets are recovered and reused as a ceramic material. However, reuse is often limited because, for example, nonuniformity in dielectric properties of a dielectric material obtained after firing may occur due to a difference in particle size distribution after redispersion, and components of the electrode applied by printing and remaining on the ceramic green sheets may function as impurities to adversely affect the properties of the dielectric material.
Thus, waste products of titanate ceramic materials primarily including barium titanate are generated. A method for effectively reusing the waste products has been studied.
A carbon-dioxide-gas absorber including at least one selected from the group consisting of lithium silicates represented by the general formula LixSiyOz is disclosed as a carbon-dioxide-gas absorber for use in separating a carbon dioxide gas (CO2) at high temperatures, the gas being emitted from automobiles and energy plants using fuel primarily including hydrocarbons (see Japanese Unexamined Patent Application Publication No. 2000-262890 (Patent Document 1)). This carbon-dioxide-gas absorber is lightweight and acts as a carbon dioxide gas at temperatures above about 500° C.
However, the volume of lithium silicates changes substantially when lithium silicates absorb and evolve a carbon dioxide gas. Thus, stress caused by repeated use disadvantageously reduces the strength of the absorber. That is, a lithium silicate (Li4SiO4) has the effect of absorbing a carbon dioxide gas at high temperatures above 500° C. by reaction with a carbon dioxide gas as shown by chemical formula (1):Li4SiO4+CO2→Li2SiO3+Li2CO3  (1)
However, the absorption of a carbon dioxide gas by the lithium silicate increases the volume about 1.4 times. Thus, repeated absorption and evolution reduces strength, leading to deterioration of the lithium silicate. That is, the lithium silicate has a short service life.